This invention relates generally to combustion devices such as stoves and furnaces for burning wood and more particularly to an automatic air inlet control to control the flow of combustion air into the combustion chamber of said combustion devices so as to reduce and limit the heat losses incident to the flow of hot air and hot combustion gases from the combustion device.
Stoves and other combustion devices generally include a combustion chamber therein which has at least one air inlet for combustion air and a discharge outlet or flue for hot air and hot combustion gases. These devices may have some air leakage or may be substantially air tight. However, even where some air leakage occurs, the greater portion of the air to support combustion enters through the combustion air inlet and conventionally some form of control device will be provided to control the flow of combustion air into the combustion chamber of the stove or like combustion device.
Those skilled in the art will readily recognize that as the rate of combustion increases, that the pressure of the draft caused by the flow of hot air and hot combustion gases through the discharge outlet or flue will also increase thereby causing a pressure drop in the combustion chamber of the given stove or like combustion device. This in turn tends to increase the flow of combustion air into the combustion chamber producing a corresponding increase in combustion in the combustion device. If this increased combustion is not controlled by providing a combustion air inlet control, the fuel which is generally wood in devices of this type, will be rapidly consumed and extensive heat losses will occur due to the waste heat which passes with the increased flow of hot air and hot combustion gases out of the combustion device through the discharge outlet or flue therefore.
If the combustion air inlet control is of the manual type, then it is obvious that the combustion will have to be manitored carefully and this will require the time and effort of a person in the vicinity of the stove or like combustion device.
In the prior art various types of combustion air inlet control devices have been developed as is shown in U.S. Pat. Nos. 1,286,489, 1,626,228, 2,232,981, 2,424,154, and 4,174,941.
In some instances other types of draft controls have been developed which act to cool the temperature of the hot air and hot combustion gases passing through the discharge outlet or flue for the combustion device as is shown in U.S. Pat. Nos. 218,596, 687,483, 1,783,418 and 1,822,321.
Where the control device is associated with the discharge outlet or flue for the combustion device, it cannot act to limit or reduce the waste heat lost in the system but merely dampens the rate of combustion in the combustion chamber of the given combustion device.
The present invention seeks to provide a relatively simple and cheap automatic air inlet control which is responsive to the pressure in the combustion chamber of the stove or like combustion device so that the air inlet control acts immediately to reduce the combustion air delivered to the combustion chamber to a predetermined minimum flow whenever increase in combustion produces a correspondingly large increase of flow in the hot air and hot combustion gases passing through the discharge outlet or flue for the combustion device. Conversely the air inlet control in accordance with the present invention will also act immediately to move to full open position when combustion air is needed to maintain combustion of the wood or other fuel in the combustion chamber of the combustion device as a function of the decrease in the flow of hot air and hot combustion gases through the discharge or flue for the combustion device.
This is accomplished in the present device by means of an elongated tubular member which is connected about the combustion air inlet for the combustion device to define an air intake flow passage therethrough in turn controlled by a damper assembly at the inlet end of the elongated tubular member which is movable from a substantially closed position wherein a predetermined minimum flow of combustion air occurs to a predetermined maximum position so as to deliver combustion air for maintaining combustion of the wood or other fuel in the combustion chamber of the combustion device.